It has recently been demonstrated that the restenosis of coronary arteries following balloon angioplasty can be prevented by irradiation of the previously stenotic area using small radioactive sources attached to the ends of catheters. Whether beta or gamma emitters, the biologically-significant doses delivered by these sources do not extend beyond several millimeters, and conventional methods of dosimetry are both impractical and lack the spatial resolution necessary to fully characterize their dose distributions. This project aims to provide a unique solution to the problem of quick and thorough characterization of these sources. A microscopic tomographic optical laser scanner will be developed, which will measure, with spatial resolution of 100 microns per pixel, full 3D dose distributions produced by these sources when inserted directly in the BANG polymer-gel dosimeter - our proprietary tissue-equivalent gel material whose optical attenuation increases linearly with absorbed radiation dose. In Phase I the feasibility will be demonstrated by building a simple prototype scanner and analyzing its performance, including spatial resolution and uniformity, accuracy, and minimum time needed for adequate data acquisition. Data obtained from this scanner will be compared with data generated by currently used techniques such as thermoluminescent crystals or radiochromic film, and with NMR microimaging. PROPOSED COMMERCIAL APPLICATION It is estimated that initially about 10,000 sources will need a thorough QA in the US. If each QA gel is priced at dollars 50, the sales of gels alone would produce dollars 500,00 annual revenue. About 25 micro scanners will be sold per year at a dollars 10,000 per scanner, yielding an additional dollars 250,000 annual revenue.